FIG. 1 shows a conventional pixelated OLED device 100. Pixelated OLED devices can be used as displays in various consumer electronic products, including cellular phones, cellular smart phones, personal organizers, pagers, advertising panels, touch screen displays, teleconferencing and multimedia products, virtual reality products, and display kiosks.
Typically, the OLED device comprises a functional stack of one or more organic functional layers 110 between a transparent conductive layer 105 and a conductive layer 115. The functional stack is formed on a transparent substrate 101. The conductive layers are patterned to form rows of cathodes in a first direction and columns of anodes in a second direction. OLED pixels are located where the cathodes and anodes overlap. Bond pads 150 are coupled to the cathodes and anodes to control the OLED pixels. A cap 160, which forms a cavity 145 between it and the pixels, encapsulates the device to protect the OLED pixels from the environment such as moisture and/or air.
In operation, charge carriers are injected through the cathodes and anodes for recombination in the functional layers. The recombination of the charge carriers causes the functional layer of the pixels to emit visible radiation.
To provide a display with high resolution and high filling factor, the spacing between pixels should be small, for example, about less than 50 μm. The spacing between the pixels is defined by the patterning processes that form the cathodes and anodes. Various conventional patterning techniques have been used to form the cathodes, such as shadow masking, photolithography (with wet or dry etching), laser ablation, or lift-off techniques (wet or dry resists). However, conventional patterning techniques are not fully compatible or feasible for fabricating OLEDs. For example, photolithographic techniques employ chemicals which damage the organic functional layers or cathode materials. With shadow masking or lift-off techniques (wet resists as well as dry resist foils), high resolutions (e.g., less than 50 μm) are difficult to achieve, particularly in a manufacturing or production environment.
As evidenced from the above discussion, it is desirable to provide a patterning technique to pattern a conductive layer which achieves high resolutions without damaging already deposited materials.